Equifax holds data of more than 820 million consumers and more than 91 million businesses worldwide, according to its website. The U.S., U.K. and Canada are its biggest markets.

Equifax(EFX) tracks and rates the financial history of consumers. The company gets its data from credit card companies, banks, retailers and lenders -- sometimes without their customers knowing.

It revealed last week that 143 million Americans could be affected by a data breach, which compromised names, Social Security numbers, birth dates, addresses, and the numbers of some driver's licenses.

Several major British and Canadian companies use Equifax to perform credit checks.

British Gas and BT(BT) in the U.K., and TD(AMTD) and CIBC in Canada are among Equifax's biggest customers.

Equifax operates in at least 24 countries globally. It said it has no indication that personal information of consumers in any other country apart from the U.S., U.K. and Canada was impacted.